The present invention concerns a device for attaching the strands of a wristband or bracelet to a case, and particularly to the middle part of a watchcase. The invention concerns more particularly a device of this kind wherein the attaching means leave free a portion of the middle part between zones for anchoring the wristband strands, while allowing said wristband to be easily interchanged, without having to use special tools.
A watch wristband is generally attached to the case by means of bars which pass through the ends of the wristband strands and are fixed to horns secured to the middle part or to extensions of said horns.
These bars are usually so called xe2x80x9cspringxe2x80x9d lugs, including a tube housing a helical spring pressing at each end on two pivots which can thus be compressed and pulled back to lock into blind recesses provided in the horns. With such a system of attachment, the wristband can only be replaced by a professional using a special tool, for example tweezers. This system is thus ill suited to current market tendencies (large scale distribution, mail-order selling), which less and less frequently require professional intervention for banal operations, and to the requirements of the consumer who may wish to replace the wristband himself at any time of the day with another wristband, for example to match his clothing.
The attachment devices disclosed in U.S. Pat. Nos. 4,561,077 and 4,624,581 provide a solution in that attachment is achieved using a hinge, which, on extensions of the middle part and on the ends of the wristband strands, includes two series of overlapping teeth, the assembly being secured by a metal rod passing through the two rows of teeth, driven into the teeth of the wristband and free to rotate in the teeth of the middle part.
In order to replace the wristband, the rod simply has to be pushed back into place, for example using another rod or the point of a needle.
Other devices for attaching a wristband to a case have also been proposed or used, amongst which those disclosed in the following documents can be cited in a non-limiting manner.
In Swiss Patent document No. 350610, the bar is also a metal rod, but has a central thinned portion allowing it to be bent and its ends to be engaged by force into blind holes provided in the horns. Swiss Patent document No. 682875 provides only one blind hole, the other hole being open onto the middle part to enable the rod to engage therein and then be held in place by being screwed from the back cover. In Swiss Patent No. 503311, a metal lug, of generally open rectangular shape, is embedded in each wristband strand end to snap into blind holes provided in the middle part. German Utility Model No. 8 509 275 discloses an attachment device wherein the lower face of the end of each wristband strand includes studs, which engage in recesses of an extension of the middle part and are locked in by staples passing through said studs and recess along a direction parallel to the back cover of the case.
It can be seen that in all these attachment devices, a part of the attachment element, bar, rod or metal lug always passes in front of the middle part at the 6 o""clock or 12 o""clock positions, which may present drawbacks in certain applications, for example for positioning a lens of a micro-camera, integrated in a watchcase, on the middle part. It will also be observed that these attachment devices, which enable a wristband to be replaced without intervention by a professional, are generally unattractive, or at least visible when the watch is worn on the wrist.
The main object of the invention is thus to overcome the drawbacks of the aforecited prior art by providing a device for attaching wristband strands to a case which enables an ordinary user to change the wristband easily, which does not detract from the aesthetic appearance of the watch and which can preferably leave portions of the middle part at 12 o""clock and/or 6 o""clock free of any attachment element.
The invention therefore concerns a device for attaching wristband strands to each side of the middle part of a watchcase without horns, closed by a back cover and by a crystal delimiting a space in which at least a watch movement is housed for a digital or analogue time display. The inner surface of each wristband strand end includes at least two studs extending perpendicularly to said surface and each being pierced in their median part by a hole along a direction parallel to the length of the strand. Each side of the middle part includes at least as many recesses as studs, complementary to the studs, in inner volume and positioning, each recess having in its median part perpendicular to the back cover of the case, a through passage on the back cover side and a blind hole on the crystal side. After the studs have been fitted into the recesses, each strand is secured to the middle part by engaging a staple, including as many branches as studs, through the through passages, the holes of the studs and the blind holes.
Before setting the securing staple in place, each wristband strand is positioned perpendicularly to the back cover. By simply pressing with the fingers along the 6 o""clock-12 o""clock direction, it is easy to fit the studs into the recesses, an operation which would be more difficult to perform if the studs were located at the very end of the strand.
The studs are preferably made of a plastic material and the holes which pass through them have a slightly smaller diameter to that of the branches of the staple, which enables said staple to be locked in after being set in place. Conversely, the through passage and the blind hole of the middle part have a slightly greater diameter to that of the branches of the staple, which reduces the effort required to remove it when the user wishes to replace the wristband.
According to a preferred embodiment, the staple has only two branches and the wristband strand two studs, such that the portion of middle part located between the two attachment zones is entirely free of any attachment means. The attachment device according to the invention thus has the advantage of making the middle part portions located substantially at 12 o""clock and 6 o""clock accessible for other arrangements. In the case of a calculator or diary watch having a keyboard on a wristband strand, the device allows the electric connections to be more easily made through a hole made in the middle part. In the case of a camera watch, it is possible to arrange the lens at the 12 o""clock position by providing a U-shaped scalloping in the end of the wristband strand.